With a recent trend of reduction in size and an increase in density of electronic equipment, double-sided circuit boards or multi-layered circuit boards are increasingly employed in place of conventional single-sided circuit boards in the field of circuit boards on which electronic components are mounted. Also, high-density circuit boards capable of mounting as many circuits as possible thereon are being developed.
As for the high-density circuit boards, design rules for circuits are becoming stringent and are requiring finer processing techniques for forming the circuits as compared with the conventional circuit boards. Regarding the multi-layered circuit boards, progress is continuously made for the development of interstitial circuit connection, through-hole and via-hole positioning techniques, and fine-pitch interstitial connection techniques.
However, as the design rules for circuits are becoming increasingly stringent, the sizes of circuit patterns, diameters of through-holes or via-holes in circuit boards, and the values of allowable applied current are becoming increasingly smaller.
In the case of an ordinary electronic circuit, the values of current flowing in each component in the circuit vary and, for example, large current values are required for power supply circuits. Although the value of current flowing in a signal circuit or the like is very small, the design rule for the circuit is required to be finer because of circuit complications and requirements for a reduction in size of electronic equipment.
Thus, in the present circuit boards, it is required to form circuit patterns through-holes or via-holes ranging from a large size to a small size in one sheet of a circuit board.
In an ordinary circuit board, a paste printing method or a photolithography method is employed for forming circuit patterns. Accordingly, it is not too difficult to form circuit patterns ranging from a large size to a small size together.
However, in forming through-holes or via-holes which have different diameters, it is necessary to use a drilling machine having multiple axes in which drills of different diameters can be used during a drilling operation. Also, in the case of drilling by using a laser beam, it is necessary to adopt a plurality of machining conditions for each of the diameters or to control the diameters by spiral scanning of the laser beam. Further, in a case of a laser process using an image transfer method, it is necessary to use a plurality of masks having a plurality of diameters, and the machine configuration becomes complicated, thereby preventing high speed machining and increasing the cost of manufacturing.
Also, data by which the finishing coordinate position in the substrate is indicated to the drilling machine is usually called NC data which is stored in paper tape, electronic medium or the like. The data becomes complicated and increased in quantity when the sizes of diameters increase, thereby requiring much more time for preparation of the data.
In the production of circuit boards, a plurality of circuit boards are arranged within a standard work size, and a tool pattern used in the manufacturing process is located at the periphery of the work size. The tool pattern includes test patterns for monitoring the board characteristics and guide marks for positioning the board in the manufacturing process.
Also, positioning marks and the like for mounting electronic components on the circuit board are often formed on the circuit boards.
However, although it is not necessary to miniaturize such guide marks at the same level as for higher-density circuit boards, it is convenient for the marks to have a specific size appropriate for their recognition.
For example, when via-holes for interstitial connection are formed in the substrate material by using a laser beam, currently available techniques are able to manufacture holes having minimum diameters ranging from 80 to 50 μm for extra-high-density circuit boards. However, if guide marks or the like are formed in such diameters, it is difficult to recognize the mark positions and, therefore, guide marks or the like are usually formed in diameters of 200 μm or more. To achieve the purpose, an exclusive machine and machining system for forming fine holes are employed to make holes with large diameters for guide marks, causing losses with respect to the time and cost.
In a high-density circuit board, it is necessary to make hundreds of thousands of fine holes per square meter and, thus, tens of thousands to hundreds of thousands of holes for via-holes are formed per sheet of a work size.
On the other hand, only about several tens of holes per sheet of a work size are formed for guide marks. Thus, there arises a problem of a decrease in a drilling efficiency because of the operation required for making a small number of guide mark holes having large diameters.
In order to address such a problem, the present invention is intended to provide a method of manufacturing a circuit board and manufacturing data by which both fine holes and large holes can be efficiently formed by using one drilling system.